The invention relates generally to fiber optical gyroscopes. In particular, the invention relates to devices designed to resolve very small angular shifts by quantum weak measurements.
A fiber optical gyroscope (FOG) measures or maintains orientation, analogous to the function of a mechanical gyroscope based on the principles of conservation of angular momentum. The FOG's principle of operation is instead based on the interference of light that passes through a coil of an optical fiber, and contains no moving components. FOGs have been employed for inertial navigation in guided missiles.
In a conventional FOG, a laser emits a beam of photons that are separated by a beam splitter into two polarized beams. Both beams enter into a single optical fiber but in opposite directions. Due to the Sagnac effect, the beam travelling against the rotation experiences a slightly shorter path delay than the other beam. Interferometry enables the resulting differential phase shift to be measured. This translates one component of angular velocity into an interference pattern shift that can be measured photometrically.
Beam-splitting optics launches light from a laser diode into two waves propagating in the clockwise and counter-clockwise directions through a coil consisting of many turns of optical fiber. The Sagnac effect's strength depends on the effective area of the closed optical path, and thus relates to the geometric area of the loop and the number of turns in the coil.